2003 Yukon clunking in 4HI and 4LO under load

[Marc Ohmann]

My wife's '03 Yukon has a clunking or skipping noise coming from the transfer case area when in 4WD and under load. It happens in both 4hi and 4lo but not in 2wd.

 

I just replaced both front hubs and that eliminated a separate clunk from the front but this is definitely coming more from the tcase area. The encoder ring went bad last winter and I'm guessing the random shifts into 4hi and 4lo from that may have caused some transfercase issues. When I did the encoder ring, the front u-joints and splines looked fine. Ujoints are original. Does clunking under load sound like a tcase issue? To me it makes sense. Or is there anything else I should check? 

[Marc Ohmann]

I'll add that when it clunks, it only does it under load and I don't notice any slippage -- the truck just keeps powering forward. But it is a repetitive clunk like a slipping and catching. Or it could even sound like the driveshaft hitting something as it spins but for that to happen only under load, the tcase would have to move and that doesn't seem likely. 

Edited July 7, 2022 by Marc Ohmann

[richard wysong]

it may be the chain inside the tc is stretched and skipping on the sprockets. if it is it will have probably damaged the rear case. not a hard repair but parts can get pricey. Transtar parts are more reasonable than oem and easier to source but they don't sell to the public so you may have to get your local parts store or garage to order them for you

[Marc Ohmann]

Thanks for the info Richard! A chain skipping seems to make sense. I guess I have to tear into it first to find out what parts it'll need. I can't think of any way to ensure it's the tcase but seems high enough probability so I should just drop it and dig into it I guess. Looks like $350 for a rebuild kit without gears or case parts. 

[richard wysong]

it is possible to repair it without removing it but it is easier on the bench. what does a rebuild kit consist of? I'm guessing oil pump seals and bearings, chain?

[Marc Ohmann]

The kit I was looking at is chain, bearings, pump, seals and clutch steel

https://www.rigidaxle.com/products/gm-np246-transtar-transfer-case-rebuild-kit-w-bearing-chain-pump-clutches-steel?currency=USD&variant=7475189317660&msclkid=bc0019cca20b11c520c67b0489f70728

 

I guess there unknowns are pinholes around the pump in the rear housing and wear on the chain drives

[dna9656]

Go look at https://www.merchant-automotive.com/

They offer parts and a fix for the pump wearing a hole in the case. My Tranny guy used some thing that in theory is the same thing as https://www.merchant-automotive.com/ fix. His fix is a sheet metal shield, I liked the fix from Merchant better. You can prolly JB Weld the holes in your T case. My tranny guy showed me many burned up T cases due to holes in the case at the pump location that allowed lube to escape and the case running dry. Auto Zone sells complete cases....

[Marc Ohmann]

Thanks dna! The wife is leaving for a week with her truck so I'll have some time to research options. I'll probably even check the junk yards to see if I can get a temp one to throw in while I get parts and finish the rebuild.